WASHINGTON (CNN) -- Secretary of State Condoleezza Rice said Thursday that proving North Korea's claims of its past nuclear activities is likely to take a long time, but establishing a process to do so could advance a long-stalled nuclear agreement.
"Verification takes some time, because these are complex programs," Rice told reporters. "This is a non-transparent society. There is a history here of surprises. What we need to know is that we've got appropriate means for verification."
A team of U.S. officials will be traveling to Pyongyang shortly to negotiate details over how to verify the long-awaited North Korean accounting of its nuclear activities, Rice said.
If the talks succeed, North Korea could produce a "declaration" of its nuclear history by the end of the month as part of a deal the United States has been working on with Pyongyang, senior officials told CNN last week.
In the deal being discussed, North Korea would finish disabling its nuclear reactor and provide a full accounting of its plutonium stockpile, the officials said.
In an addendum to the main agreement, North Korea also would "acknowledge" concerns about its proliferation activities and its uranium enrichment activity and agree to continue cooperation with a verification process to ensure no further activities take place.
In exchange, the United States would remove North Korea from its State Sponsors of Terrorism list and would remove sanctions in place under the Trading With the Enemy Act -- actions Pyongyang has long sought.
Those steps are part of phase two of a three-phase deal reached through a process referred to as the "six-party talks" -- involving North Korea, South Korea, China, Russia, Japan and the United States -- aimed at denuclearizing the Korean peninsula.
The United States softened its demand that North Korea publicly admit to having a highly enriched uranium program and to providing Syria with nuclear technology, key issues that stalled negotiations for months.
Officials told CNN the United States concluded it is more important to get a handle on the program than to have North Korea "confess" past nuclear sins.
In recent weeks, Rice suggested verifying North Korea's claims is more important than the actual document itself.
"It will take some time, even past the second phase, for verification to completely play out," she said Thursday. But she said if North Korea meets its obligations under the deal, the other parties are prepared to respond with the promised rewards.
The original agreement in the six-party talks did not deal with proliferation, but Rice said it was important to do so "in light of some recent concerns about North Korean activities in proliferation."
"Syria is most certainly an issue in proliferation," she said, adding, "We have several non-proliferation questions on on the table about North Korea."
If the deal goes through, it would pave the way to move to the third part of the six-party agreement, which requires North Korea to permanently dismantle its nuclear reactor and destroy its plutonium stockpile.
"If it's demonstrated in phase three that somehow something was wrong in phase two, of course the United States reserves the right to take whatever steps it needs to, even if we've declared phase two complete," Rice said. E-mail to a friend